The original books missed the idea of initial motivation on the "adventurer" career path. Why and how did even these first level characters end up this way. That makes the rules and settings awkward and necessitates the world to contain bait for first level characters. Like posters seeking guards for (incompetent) caravan escort duty or that kind of thing. Some people noticed that and tried to formulate 1st level adventures or entire world settings which did not start with a fully formed 1st level fighter or mage. Perhaps you start as a bored teen farm hand, or something extraordinary happens in your life but it helps if there is something that kicks you outside of "normal" medieval life and into something far more individualistic.